The subject matter of the present invention concerns polymeric transition-metal complex catalysts with organosiloxane diphenylphosphine ligands which are present as formed copolycondensates. The formed, polymeric, insoluble complex compounds of Fe, Co, Ni, Ru, Rh, Pd, Os, Ir and/or Pt exhibit the engineering and application-technology advantages of a macroscopic spherical form and have the physical properties necessary for use as heterogenized complex catalysts. Methods are also described according to which the novel products can be prepared not only in the spherical size desired for the particular use but also with the suitable physical properties. In addition, the use of these polymeric catalysts is described.
Homogeneous catalysts that are used exhibit without exception a higher activity and selectivity than comparable heterogeneous catalysts. However, rather significant engineering problems generally occur in the use of these catalysts in connection with their separation of the formed product from solvent present and with their recycling. Moreover, the recovery of the expensive noble-metal component from the residues of the reaction mixture is expensive and can normally only be carried out with rather significant metal losses.
Another disadvantage of homogeneous catalysts that are used is the frequently rather short residence time caused by the formation of catalytically inactive species.
In order to circumvent the above described disadvantages of so-called homogeneous catalysts, there has already been followed for some time worldwide the development of so-called heterogenized homogeneous catalysts (heterogenized catalysts) in which the homogeneous catalyst normally used is bound to a solid carrier.
The state of the art in this area of catalysis has already been summarized in appropriate survey literature, e.g. by R. H. Grubbs in CHEMTECH, Aug. 1977, p. 512 by F. R. Hartley in "Catalysis by Metal Complexes", D. Reidel Publ Co., 1985; or also by Yu. I. Yermakov et al. in "Catalysis by Supported Complexes", Elsevier Scientific Publ. Co., 1981.
However, up to the present, for a number of reasons the organic and inorganic polymer systems used as carrier materials have met the desired requirements only to a very limited extent. In the case of organic polymer carriers, the physical and mechanical properties, in particular, as well as the too low chemical stability, represent disadvantages; whereas inorganic polymer carriers such as silica gel have the disadvantage of a functionality which is too low and, in addition, insufficiently defined.
Novel, heterogenized metal complex catalysts which do not exhibit the above described disadvantages of the previous systems were recently developed, as is described in German patent 30 29 599. The matrix of these polysiloxane catalysts has practically the advantages of an inorganic polymer carrier and, in addition, can be produced approximately on a made to order basis, e.g. as regards the important aspects, namely, that the metal : ligand ratio can be varied or that so-called cross-linking agents can be integrated into the matrix or that a control of the catalytic central density and distribution is possible. Compared to systems with purely inorganic carriers, these organopolysiloxane polymers display in particular the advantages of a higher metal concentration, of simpler preparative accessibility, and of greater stability vis-a-vis chemical degradation.
In particular, the polymeric metal phosphine complexes mentioned in German patent 30 29 599, which generally exhibit very good catalytic properties, were synthesized according to this concept. However, these heterogenized complex catalysts have the disadvantage that they could previously be prepared only in a relatively undefined macroscopic shape and not in the spherical form advantageous in application technology with the desired physical and morphological properties.